Free chlorine
Chlorine that has not bonded to anything yet. It is the fast germ-killer, and it fades as the water travels through miles of pipe. It also gasses off a glass of water left out overnight.
For plumbers and service techs
Chlorine or Chloramine: How to Tell What Your City Puts in the Water
Dip a free chlorine strip in a glass of tap water in Sachse, Texas and it reads close to zero. The water is not unprotected. It is protected by chloramine, and a free chlorine strip cannot see it.
Which one your city uses is a fact the city publishes. A plumber who knows it before the tap is turned on reads the strip right. One who does not tells the homeowner the wrong thing.
Short answer
Two Disinfectants, One Strip Reading
Every public water system adds a disinfectant to keep the water safe on the way to the house. Some use chlorine on its own. Some add ammonia to the chlorine, which makes chloramine (say it klor-uh-meen). The EPA says more than one in five Americans use drinking water treated with chloramines, and that chloramines are most commonly formed when ammonia is added to chlorine to treat drinking water. The city's own water quality report says which one it uses, and a two-pad test strip confirms it at the tap.
Combined chlorine
Chlorine that has bonded with ammonia. That bond is chloramine. It is weaker but it holds its strength far down a long pipeline, which is why big regional systems use it. It does not gas off a glass left out overnight.
Total chlorine
Free plus combined. It is the number most city reports print, and it is the number that belongs on the customer's copy of a water test.
Three ways to know
How to Find Out Which One Your City Uses
Read the water quality report
Every public water system publishes one each year. Find the disinfectant row. The City of Sachse's 2025 Annual Drinking Water Quality Report prints it on page 3 as "Chlorine Residual (Chloramines)," average 2.48 parts per million, range 0.60 to 3.8. That is the city saying the word. Nothing else is needed.
If the report does not say, call the district
Some reports print only "Total Chlorine Residual" and never name the disinfectant. The Carlsbad Municipal Water District's report is one: 0.33 to 3.50 parts per million at the district's own taps, no word on which kind. The district told the HALO Water Tour by phone that its water is chloramine. A phone answer from the district is a source, and it is cited as a phone answer, not dressed up as something the report said.
Confirm it at the tap with a two-pad strip
Run the cold tap first. Fill a clean cup. Dip a strip that has both a free chlorine pad and a total chlorine pad. Read both. The gap between them is the answer, and the table below reads it for you.
Reading the strip
What the Two Pads Tell You
| Total pad | Free pad | What it means |
|---|---|---|
| 1 ppm or more | About the same as total | Free chlorine. The city uses chlorine on its own and almost all of it is still free when it reaches the house. |
| 1 ppm or more | Near zero | Chloramine. The chlorine is bonded to ammonia, so the free pad cannot see it. The water is disinfected; the strip just needed the right pad. |
| Near zero | Near zero | No residual at the tap. On a private well that is normal. On city water, run the tap longer and test again; if it stays at zero, call the district. |
ppm is parts per million, the same unit the city reports use. Write the total chlorine number on the customer's copy. The free number is for you, to confirm which kind.
Why a plumber cares
Why the Kind Matters More Than the Number
A homeowner smells chlorine in the shower and asks what can be done about it. The answer depends on which disinfectant is in the water, because the two are not removed the same way. Chloramine holds its bond. Equipment that handles free chlorine easily can let chloramine through. Which equipment handles which is Day Two of the HALO Water Tour, and it starts with the plumber knowing which one the house has.
It also changes the conversation at the sink. In Sachse the plumber can show the homeowner their own city's report, point at the word "Chloramines," then show the strip: total pad colored, free pad blank. The homeowner just watched the city's own report and the water in their glass agree with each other. Nobody sold anything.
Where it goes wrong
Four Ways to Get the Disinfectant Wrong
Reading only the free pad
The most common mistake. In a chloramine town the free pad reads near zero and the tech announces there is no chlorine in the water. The report on the counter says otherwise.
Trusting the smell
Both disinfectants smell like chlorine. A nose cannot tell them apart. The report and the total pad can.
Assuming one answer for the whole metro
A city can be served by more than one district, and each publishes its own report. The City of Carlsbad is served by three. Read the report for the district that serves this house.
The overnight glass
A customer leaves a glass out overnight to let the chlorine go away. Free chlorine does leave. Chloramine does not. If their city uses chloramine, the glass in the morning has the same disinfectant it had the night before.
Two real reports
The Same Question, Two Different Answers From the Paperwork
Sachse, Texas
The 2025 report names it: "Chlorine Residual (Chloramines)." Average 2.48 parts per million, range 0.60 to 3.8. The water comes from the North Texas Municipal Water District's surface water, which travels a long way, and chloramine is built for that trip. A plumber in Sachse knows the answer before the truck starts.
Carlsbad, California
The Carlsbad Municipal Water District's report prints "Total Chlorine Residual" and stops there. The water is a blend of imported water and desalinated water. The district confirmed chloramine by phone and has nothing in writing. A plumber in Carlsbad cites the district's phone answer and confirms it with the two-pad strip at every house, because the report alone cannot (see our Carlsbad water guide).
For Dallas, see our Dallas water guide. For the hardness figures each utility publishes, see water hardness by city.
Watch it done
Roger on Reading the Report Before You Test
Questions
Chlorine and Chloramine Questions
How do I know if my tap water has chlorine or chloramine?
Read your city's annual water quality report and find the disinfectant row. Some reports name chloramine outright; some print only a total chlorine residual. If yours does not name it, call the water district and ask. At the tap, a strip with a free chlorine pad and a total chlorine pad tells you: if the two read about the same, it is chlorine; if total reads 1 part per million or more and free reads near zero, it is chloramine.
What is chloramine?
Chloramine is chlorine bonded with ammonia. Cities make it on purpose by adding ammonia to chlorine, because it holds its strength farther down a long pipeline than chlorine alone. The EPA says more than one in five Americans use drinking water treated with chloramines.
Why does my free chlorine test strip read zero?
Because your city most likely uses chloramine. The chlorine is bonded to ammonia, and a free chlorine pad only sees chlorine that is not bonded to anything. The total chlorine pad sees both. A zero on the free pad does not mean there is no disinfectant in the water.
Does letting tap water sit overnight remove chloramine?
No. Free chlorine gasses off a glass left out overnight. Chloramine holds its bond and stays. If your city uses chloramine, the glass in the morning carries the same disinfectant it did the night before.
Does the HALO Water Tour teach how to tell chlorine from chloramine?
Yes. Day One teaches reading the city's water quality report, including the disinfectant row, and testing the water at the tap. Day Two covers which problems each type of equipment solves, including the difference between removing chlorine and removing chloramine. A certification exam closes every day.
Sources
Where These Facts Come From
Checked in October 2026. Reports are reissued every year, so confirm with the source before you rely on a number.
- U.S. EPA, Chloramines in Drinking Water (more than one in five Americans; how chloramines are formed)
- City of Sachse, 2025 Annual Drinking Water Quality Report (page 3, Chlorine Residual (Chloramines); page 1, water source)
- Carlsbad Municipal Water District, Water Quality Report (page 2, Total Chlorine Residual; page 1, water sources)
- Carlsbad Municipal Water District by phone to the HALO Water Tour, 26 September 2026: chloramine, nothing in writing
- The sixty-second water test, Carlsbad water quality guide and Dallas water quality guide on this site
Written by Roger Wakefield, Texas Master Plumber
45 years in the trade and LEED AP. Published . More about Roger or visit rogerwakefield.com.
Keep going
Related Guides
The sixty-second water test
Report first, then hardness, total chlorine and TDS at the tap.
How to become a water quality expert
What the credential covers and how a plumber earns it.
Carlsbad water quality
Imported and desalinated water, and why the blend matters at the tap.
Dallas water quality
What the city reports and what Roger reads in Dallas homes.
Learn to read the report, test the water and explain it in three days
Three consecutive days, in person, twenty seats a city: Carlsbad October 27-29 and Dallas November 3-5, 2026. A certification exam closes every day, and the HALO Certified Water Quality Expert credential is awarded on day three.